The Coastal National Elevation Database: Seamless Maps from Land to Seafloor

USGS Fact Sheet 2018–3037, June 2018.

The San Francisco Bay area, California, as a topobathymetric model. Image: USGS.

What CoNED is

The Coastal National Elevation Database (CoNED) Applications Project builds enhanced topographic (land elevation) and bathymetric (water depth) datasets for coastal hazards research. They are widely used to map areas flooded by rivers, hurricanes and sea-level rise, and to model sediment transport, erosion and storm impacts.

CoNED is a USGS Coastal-Marine Hazards and Resources Program activity based at the Earth Resources Observation and Science (EROS) Center. As part of the vision for a 3D Nation, it works with the USGS National Geospatial Program, NOAA and the U.S. Army Corps of Engineers, through the Interagency Working Group on Ocean and Coastal Mapping, to merge land topography with nearshore and continental-shelf bathymetry. Partners include the Interior Pacific Islands Climate Adaptation Science Center, the National Park Service, The Nature Conservancy, Louisiana's Coastal Protection and Restoration Authority and many universities.

Goals

CoNED's main product is the seamless, cross-shore topobathymetric digital elevation model (TBDEM), for coastal and marine spatial planning. It also extends the USGS 3D Elevation Program (3DEP) to the ocean coasts and Great Lakes. Its aims:

• better understand and predict how coasts respond to sea-level rise, climate change and development;
• build TBDEMs in focus regions for research and planning;
• provide seamless TBDEMs from the shore out to the 3-nautical-mile limit offshore, using new methods such as land–water masking and multi-date frameworks to combine data.

Where TBDEMs exist

TBDEMs are built from many topographic and bathymetric sources, aligned to a common reference. The first high-resolution one, in 2012, covered Mobile Bay, Alabama, the nation's fourth-largest estuary. Others cover Chesapeake Bay, Delaware, New England, New Jersey, the Northern Gulf of Mexico, Central and Southern California, Puget Sound, the Pacific Northwest, Alaska's North Slope and Majuro Atoll in the Marshall Islands.

The northern Gulf of Mexico, including Mobile Bay, Alabama. Image: USGS.

The science it supports

• Storms and wetlands: TBDEMs span land and sea, so they serve research on coasts hit by hurricanes in the east and Gulf and extratropical cyclones in the west. CoNED scientists mapped complex wetland and open-water patterns for storm-surge and sediment models, shoreline change and wetland maps. Because the accuracy of land elevation drives the reliability of sea-level rise and inundation assessments, TBDEMs are key.
• Sea cliffs: with high-resolution lidar point clouds, TBDEMs have improved measurement of volume change where sea cliffs and bluffs threaten homes and infrastructure; automatically extracted cliff profiles help communities plan.

Monterey Bay, central California. Image: USGS.

• Pacific islands: lacking data, researchers made land elevation from Structure-from-Motion point clouds from drone photos, and depths from Landsat and WorldView satellite imagery.
• Alaska: lidar from 2009 to 2012 along the north coast set a modern shoreline for tracking change and hazards.

Majuro Atoll, Republic of the Marshall Islands. Image: USGS.

Sources

Based on Coastal National Elevation Database, USGS Fact Sheet 2018–3037, U.S. Geological Survey; a work of the United States government in the public domain. The four TBDEM images are taken from the fact sheet's PDF.